A monstrously huge creature that washed ashore on a remote Indonesian beach, oozing a mysterious red fluid, is probably a baleen whale in an advanced state of decomposition, experts said.

The nearly 50-foot-long marine creature was lying on Hulung Beach on Seram Island, Indonesia, and was first discovered by 37-year-old local resident Asrul Tuanakota, who initially mistook the creature for a boat, the Jakarta Globe reported.

Despite the blob's bizarre appearance, it's clearly a baleen whale, said Alexander Werth, a whale biologist at Hampden-Sydney College in Virginia.

"There is lots of stuff in the ocean that we don't know about — but there's nothing that big" that remains unknown, Werth said.

Two dead giveaways revealed that the creature was a whale, Werth said: the grooves, or "throat pleats," and the upper jaw where the two racks of baleen plates, used for filtering out food in the whale's mouth, would have been. [Whale Photos: Giants of the Deep]